Guiyu oneiros

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Guiyu oneiros
Temporal range: Late Silurian,
425.6  Ma [1]
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Guiyu oneiros.png
Skeletal reconstruction
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Superclass: Osteichthyes
Genus: Guiyu
Zhu et al., 2009
Species:
G. oneiros
Binomial name
Guiyu oneiros
Zhu et al., 2009

Guiyu oneiros is one of the earliest articulated bony fish discovered. Fossils of Guiyu have been found in what is now Qujing, Yunnan, China, in late Silurian marine strata, [2] about 425 million years old. [1]

Guiyu is part of the Xiaoxiang fauna which is rich in fossils representing a marine ecosystem. Found in the late Ludlow-aged Kuanti Formation, the remains were dated using conodonts as index fossils. The Xiaoxiang fauna also includes galeaspids, placoderms and acanthodians. [3]

Discovery and naming

Guiyu was described by Chinese palaeontologist Zhu Min (朱敏) and others in 2009, based on a near-complete articulated specimen. The generic name Guiyu is a transliteration of the Mandarin 鬼魚 guǐyú "ghost fish" and the specific name oneiros is from Greek ὄνειρος "dream". [2]

Description

Specimen on display at the Paleozoological Museum of China Guiyu oneiros PMC.jpg
Specimen on display at the Paleozoological Museum of China

The holotype specimen is about 26 centimetres (10 in) in length and about 11 centimetres (4.3 in) in depth. The caudal fin has not been preserved, and the living fish is estimated to have been around 30 centimetres (12 in) long. [2] The head made up about 23% of the body length, and the body had a streamlined shape. [2] It possessed several primitive features characteristic of placoderms (jawed stem-gnathostomes) but missing in modern osteichthyans. While the pelvic girdle of modern osteichthyans is made exclusively of endochondral bone, the pelvis of Guiyu included dermal bones as well, including paired lateral plates and an unpaired median plate. [4] The pectoral, pelvic and dorsal fins bore large spines, as seen in many placoderms and acanthodians (basal stem-chondrichthyans). Behind the skull roof there were three median dorsal plates (bones that made up part of the thoracic armour in most placoderms), with the third plate bearing the first dorsal fin spine. [5] The skull bones, scales and other dermal bones were covered in ganoine, a tissue that also covers the scales and cranial bones in basal ray-finned fishes. [2]

Classification

Life restoration Life restoration of Guiyu oneiros.png
Life restoration

Guiyu was initially described as a basal lobe-finned fish with anatomical features of both ray-finned and lobe-finned fishes. [2] Guiyu sheds light on the early diversification of bony fishes. This clade, the osteichthyans, splits in two clades: the lobe-finned fishes (sarcopterygians) and the ray-finned fishes (actinopterygians). If Guiyu was a sarcopterygian, this split must have already occurred by the late Silurian period, no later than 419 million years ago (original estimate) [2] or 425 Ma (recent estimate). [1] Guiyu has frequently been placed in a clade with three other primitive osteichthyans ( Achoania , Psarolepis and Sparalepis ); this clade has been informally dubbed the "psarolepids". [6]

The cladogram below follows the analysis of Yu et al. (2010), which recovered Guiyu as a basal sarcopterygian: [7]

Sarcopterygii  

The many primitive features of Guiyu and other "psarolepids" have led palaeontologists to suggest that they were stem-group osteichthyans instead, lying outside the clade formed by actinopterygians and sarcopterygians. This theory had little support from phylogenetic analyses until the 2017 description of Ptyctolepis , a stem-sarcopterygian from the Early Devonian of China. The accompanying phylogenetic analysis recovered Guiyu and the other "psarolepids" as the sister group of crown-osteichthyans. A cladogram from that study is shown below: [6]

Related Research Articles

<span class="mw-page-title-main">Chondrichthyes</span> Class of jawed cartilaginous fishes

Chondrichthyes is a class of jawed fish that contains the cartilaginous fish or chondrichthyians, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or bony fish, which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opecula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.

<span class="mw-page-title-main">Osteichthyes</span> Diverse group of fish with skeletons of bone rather than cartilage

Osteichthyes, also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage. The vast majority of extant fish are members of Osteichthyes, being an extremely diverse and abundant group consisting of 45 orders, over 435 families and 28,000 species. It is the largest class of vertebrates in existence today, encompassing most aquatic vertebrates, as well as all semi-aquatic and terrestrial vertebrates.

<span class="mw-page-title-main">Gnathostomata</span> Infraphylum of vertebrates

Gnathostomata are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living gnathostomes have true teeth, paired appendages, the elastomeric protein of elastin, and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheaths of neurons, and an adaptive immune system that has the discrete lymphoid organs of spleen and thymus, and uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene.

<span class="mw-page-title-main">Sarcopterygii</span> Class of fishes

Sarcopterygii — sometimes considered synonymous with Crossopterygii — is a clade of bony fish commonly referred to as lobe-finned fish. They are characterised by prominent muscular limb buds (lobes) within their fins, which are supported by articulated appendicular skeletons. This is in contrast to the other clade of bony fish, the Actinopterygii, which have only skin-covered bony spines supporting the fins.

<span class="mw-page-title-main">Acanthodii</span> Class of fishes (fossil)

Acanthodii or acanthodians is an extinct class of gnathostomes. They are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and chimaeras. Acanthodians possess a mosaic of features shared with both osteichthyans and chondrichthyans. In general body shape, they were similar to modern sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteians.

<span class="mw-page-title-main">Placoderm</span> Class of fishes (fossil)

Placoderms are members of the class Placodermi, a group of prehistoric fish known from Paleozoic fossils which lived from the Silurian to the end of the Devonian period. While their endoskeletons are mainly cartilaginous, their head and thorax were covered by articulated armoured plates, and the rest of the body was scaled or naked depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first pair of gill arches.

<span class="mw-page-title-main">Teleostomi</span> Clade of jawed vertebrates

Teleostomi is an obsolete taxon of jawed vertebrates that supposedly includes the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key characters of this group include an operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives. The teleostomes include all jawed vertebrates except the chondrichthyans and the extinct class Placodermi.

<span class="mw-page-title-main">Arthrodira</span> Extinct order of fishes

Arthrodira is an order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches. Arthrodires were the largest and most diverse of all groups of placoderms.

<i>Psarolepis</i> Extinct genus of fishes

Psarolepis is a genus of extinct bony fish which lived around 397 to 418 million years ago. Fossils of Psarolepis have been found mainly in South China and described by paleontologist Xiaobo Yu in 1998. It is not known certainly in which group Psarolepis belongs, but paleontologists agree that it probably is a basal genus and seems to be close to the common ancestor of lobe-finned and ray-finned fishes. In 2001, paleontologist John A. Long compared Psarolepis with onychodontiform fishes and refer to their relationships.

Andreolepis is an extinct genus of prehistoric fish, which lived around 420 million years ago. It was described by Walter Gross in 1968 based on scales found in the Hemse Formation in Gotland, Sweden. It is placed in the monogeneric family Andreolepididae and is generally regarded as a primitive member of the class Actinopterygii based on its ganoid scale structure; however some new research regards it as a stem group of osteichthyans.

The Xitun Formation is a palaeontological formation which is named after Xitun village in Qujing, a location in South China. This formation includes many remains of fossilized fish and plants of the Early Devonian period. It was originally referred to as the Xitun Member of the Cuifengshan Formation.

<span class="mw-page-title-main">Evolution of fish</span> Origin and diversification of fish through geologic time

The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.

<i>Brochoadmones</i> Extinct genus of cartilaginous fishes

Brochoadmones is an extinct genus of acanthodian from the Devonian of what is now Canada. It is the only genus in the suborder Brochoadmonoidei, whose relationship to other acanthodian orders remains currently in flux.

Cosmine is a spongy, bony material that makes up the dentine-like layers in the scales of the lobe-finned fishes of the class Sarcopterygii. Fish scales that include layers of cosmine are known as cosmoid scales.

<i>Entelognathus</i> Placoderm fish from the late Ludlow epoch of the Silurian period

Entelognathus primordialis is an early placoderm from the late Silurian of Qujing, Yunnan, 419 million years ago.

<i>Megamastax</i> Extinct genus of fishes

Megamastax is a genus of lobe-finned fish which lived during the late Silurian period, about 423 million years ago, in China. Before the discovery of Megamastax, it was thought that jawed vertebrates (gnathostomes) were limited in size and variation before the Devonian period. Megamastax is known only from jaw bones and it is estimated that it reached about 1 metre long.

<i>Qilinyu</i> Extinct genus of fishes

Qilinyu is a genus of early placoderm from the late Silurian of China. It contains a single species, Qilinyu rostrata, from the Xiaoxiang fauna of the Kuanti Formation. Along with its contemporary Entelognathus, Qilinyu is an unusual placoderm showing some traits more similar to bony fish, such as dermal jaw bones and lobe-like fins. It can be characterized by adaptations for a benthic lifestyle, with the mouth and nostrils on the underside of the head, similar to the unrelated antiarch placoderms. The shape of the skull has been described as "dolphin-like", with a domed cranium and a short projecting rostrum.

<span class="mw-page-title-main">Sam Giles</span> Paleontologist

Sam Giles is a palaeobiologist at the University of Birmingham. Her research combines modern imaging with fossils to understand the evolution of life, in particular that of early fish, and in 2015 "rewrote" the vertebrate family tree. She was a 2017 L'Oréal-UNESCO Rising Star and won the 2019 Geological Society of London Lyell Fund.

<i>Bianchengichthys</i> Extinct genus of maxillate placoderm fish

Bianchengichthys is a genus of maxillate placoderm fish from the late Silurian Period. Its fossils have been recovered from Yunnan Province, China, and it is represented by only one species: Bianchengichthys micros.

Min Zhu, is a Chinese paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), a CAS Member. He completed his undergraduate studies at Nanjing University and completed his PhD thesis at IVPP. He is currently leading a research team from IVPP. The latest findings from his team are unearthed from two new fossil depositories, shedding light on the rise of jawed vertebrates

References

  1. 1 2 3 Zhao, W.; Zhang, X.; Jia, G.; Shen, Y.; Zhu, M. (2021). "The Silurian-Devonian boundary in East Yunnan (South China) and the minimum constraint for the lungfish-tetrapod split". Science China Earth Sciences. 64 (10): 1784–1797. Bibcode:2021ScChD..64.1784Z. doi:10.1007/s11430-020-9794-8. S2CID   236438229.
  2. 1 2 3 4 5 6 7 Zhu, M.; Zhao, W.; Jia, L.; Lu, J.; Qiao, T.; Qu, Q. (2009). "The oldest articulated osteichthyan reveals mosaic gnathostome characters". Nature. 458 (7237): 469–474. Bibcode:2009Natur.458..469Z. doi:10.1038/nature07855. PMID   19325627. S2CID   669711.
  3. Zhu, M.; Zhao, W. (2009). "The Xiaoxiang Fauna (Ludlow, Silurian) – a window to explore the early diversification of jawed vertebrates". Rendiconti della Società Paleontologica Italiana. 3 (3): 357–358.
  4. Zhu, Y.-A.; Wang, Y.-J.; Qu, Q.-M.; Lu, J.; Zhu, M. (2022). "The pelvic morphology of Parayunnanolepis (Placodermi, Antiarcha) revealed by tomographic data". Vertebrata PalAsiatica. doi:10.19615/j.cnki.2096-9899.221126.
  5. Zhu, M.; Yu, X.; Choo, B.; Qu, Q.; Jia, L.; Zhao, W.; Qiao, T.; Lu, J. (2012). "Fossil Fishes from China Provide First Evidence of Dermal Pelvic Girdles in Osteichthyans". PLOS ONE. 7 (4): e35103. Bibcode:2012PLoSO...735103Z. doi: 10.1371/journal.pone.0035103 . PMC   3318012 . PMID   22509388.
  6. 1 2 Lu, J.; Giles, S.; Friedman, M.; Zhu, M. (2017). "A new stem sarcopterygian illuminates patterns of character evolution in early bony fishes". Nature Communications. 8 (1): 1932. Bibcode:2017NatCo...8.1932L. doi:10.1038/s41467-017-01801-z. PMC   5715141 . PMID   29203766.
  7. Yu, X.; Zhu, M.; Zhao, W. (2010). "The origin and diversification of Osteichthyans and Sarcopterygians: Rare Chinese fossil findings advance research on key issues of evolution". Bulletin of the Chinese Academy of Sciences. 24: 71–75.